While a Mars rover
can't operate upside down, the Hedgehog robot can function
regardless of
which side lands up. Credit: NASA/JPL-Caltech/Stanford
(September 5, 2015) Hopping,
tumbling and flipping over are not typical maneuvers you would expect from a
spacecraft exploring other worlds. Traditional Mars rovers, for example, roll around
on wheels, and they can't operate upside-down. But on a small body, such as an
asteroid or a comet, the low-gravity conditions and rough surfaces make
traditional driving all the more hazardous.
Enter Hedgehog: a new concept for a robot that is specifically
designed to overcome the challenges of traversing small bodies. The project is
being jointly developed by researchers at NASA's Jet Propulsion Laboratory in
Pasadena, California; Stanford University in Stanford, California; and the
Massachusetts Institute of Technology in Cambridge.
NASA's C-9
aircraft for microgravity research gave two Hedgehog prototypes
a ride in June
2015 to test their maneuvers. Credit: NASA
"Hedgehog is a different kind of robot that would hop
and tumble on the surface instead of rolling on wheels. It is shaped like a
cube and can operate no matter which side it lands on," said Issa Nesnas,
leader of the JPL team.
The basic concept is a cube with spikes that moves by
spinning and braking internal flywheels. The spikes protect the robot's body
from the terrain and act as feet while hopping and tumbling.
"The spikes could also house instruments such as
thermal probes to take the temperature of the surface as the robot
tumbles," Nesnas said.
Two Hedgehog prototypes -- one from Stanford and one from
JPL -- were tested aboard NASA's C-9 aircraft for microgravity research in June
2015. During 180 parabolas, over the course of four flights, these robots
demonstrated several types of maneuvers that would be useful for getting around
on small bodies with reduced gravity. Researchers tested these maneuvers on
different materials that mimic a wide range of surfaces: sandy, rough and
rocky, slippery and icy, and soft and crumbly.
"We demonstrated for the first time our Hedgehog
prototypes performing controlled hopping and tumbling in comet-like
environments," said Robert Reid, lead engineer on the project at JPL.
Hedgehog's simplest maneuver is a "yaw," or a turn
in place. After pointing itself in the right direction, Hedgehog can either hop
long distances using one or two spikes or tumble short distances by rotating
from one face to another. Hedgehog typically takes large hops toward a target
of interest, followed by smaller tumbles as it gets closer.